Seth Gunar moved in the fall of 2012 from an apartment in Mahwah to a three-bedroom house in Ringwood. He had to haul his things — including a gun and rifle collection — a mere half-dozen miles. But in retrospect, the fate of two lives may well have hung on that short journey across the Bergen/Passaic county line.

Gunar’s questionable behavior had already provided law enforcement authorities with many red flags. More than a year before he fatally shot a houseguest, Chris Coogan, then himself in early February, the police in Mahwah had moved to seize Gunar’s legal gun collection, believing that he presented a threat to himself and others.

But the move from Mahwah to Ringwood by Gunar, 43, a disbarred lawyer, brought a halt to the effort to obtain a court order to remove his weapons. In the weeks since the shootings, local and county law-enforcement officials have engaged in finger pointing over how a man who drank heavily, had a history of belligerent encounters and owned at least five or six guns and rifles had been allowed to retain them.

After Gunar moved to Passaic County, the Bergen County Prosecutor’s Office closed the case it had initiated to seize his weapons, anticipating that the Ringwood police would take up the matter. Mahwah police officials notified the Ringwood police about their concerns over Gunar’s drinking and his brushes with the law. But the Ringwood police did not act because they assumed the legal case had been transferred by the Bergen prosecutors to their counterparts in Passaic County. It had not.

“He definitely slipped through a couple of cracks,” said the Ringwood police chief, Bernard Lombardo.

Early on Feb. 3, Gunar shot Coogan and then himself in his Cupsaw Drive home, hours after they had watched the Super Bowl with friends. The two had been arguing, with Gunar accusing Coogan, 23, of stealing his iPad. Friends said Gunar had been drinking all day and through the night.

For at least 18 months before the shootings, though, Gunar’s actions had brought him to the attention of local police.

In Mahwah, he threatened the manager of his apartment building on Franklin Turnpike, telling her, “I’m putting you in my book,” according to police reports. The manager reported to the police an incident in which Gunar became angry over a broken air-conditioning unit; she said a repair technician received a $10 tip from Gunar wrapped in a shell casing.

When a young woman Gunar had asked to feed his cats entered his house, she noticed many of his firearms spread out on his bed, instead of being locked safely away, according to police reports. He had also been involuntarily committed to a hospital psychiatric unit after his stepfather contacted a hotline to report that Gunar appeared to be suicidal and owned firearms, Mahwah police records show.

After he moved to Ringwood, Gunar was charged with driving under the influence after being stopped on his way to what friends called his “go-to” drinking spot in Mahwah. The police were also called to his house in Ringwood last year after a roommate claimed that a drunken Gunar punched him in the face during an argument.

Mahwah Police Chief James N. Batelli said his department’s effort to seek a court order to revoke Gunar’s firearms-purchaser identification card — issued by his department in June 2000 — was prompted by the number of incidents over a short period of time.

“I think we would have prevailed at having his weapons taken away,” Batelli said.

The Mahwah police informed their Ringwood counterparts of their concerns about Gunar after he moved there, but Lombardo, the Ringwood police chief, said he assumed prosecutors were continuing to press for a court order. He said he had not known that the Bergen County Prosecutor’s Office had closed the case and that prosecutors in Passaic County were unaware of it.

Lombardo said Ringwood was never notified it had to act on Gunar’s weapons.

“It was assumed the prosecutor’s offices were handling it amongst themselves,” he said. “We just assumed the Bergen County Prosecutor’s Office was going to contact our Prosecutor’s Office” in Passaic County.

Bergen County Prosecutor John Molinellli said his office never contacted Ringwood police. He said it was up to that department to work with Passaic County prosecutors, just as Mahwah police had contacted his office.

“Even if we had called the Prosecutor’s Office, they probably would have called the chief of Ringwood,” Molinelli said in an email. “Normally it’s the chief. That’s where it initiates.”

Once Gunar took up residence outside Bergen County, Molinelli said, his office dropped the case. “Actions commenced to revoke a gun permit may be brought by the county prosecutor or chief of police in the county/town where the gun owner resides,” he wrote. “We could not have brought such an action.”

Molinelli added, “I can’t say by any rule per se, but that is the way it always proceeded.”

The state provides no guidelines on how prosecutors should handle gun permit revocations when a gun owner moves from one county to another, said Peter Aseltine, a spokes­man for the state attorney general.

Eugene O’Donnell, a John Jay College professor of law and police studies who worked as a prosecutor and police officer in New York City, said the Gunar case highlights the risks of informal arrangements.

“You need to have systems that are fail-safe,” he said. “You can’t be relying on individuals. That’s not sufficient.”

Jef Henninger, a lawyer with offices in Clifton and other locations who represents people in gun permit cases, said the Ringwood police should have contacted the Passaic County Prosecutor’s Office to request legal help once they determined Gunar was unfit to own guns.

“Prosecutors file in court on behalf of the police chief,” Henninger said.

But another lawyer, Evan Nappen, said nothing in state law prevented the Bergen County Prosecutor’s Office from pursuing a court order to remove Gunar’s weapons even after he moved out of the county.

“There was no reason for them to not follow through because he moved,” said Nappen, who is based in Monmouth County.